Running form drills

I ran my 3 miles last night with a focus on faster leg turnover. I was attempting to run everything in the 8:30 pace range, but had trouble judging speed with the quicker cadence. Mile one was run with the pup at 8:55, he was dropped off at the homestead before the last two. Mile two was a 7:45 run at 84% heart rate. The quicker cadence raised my heart rate a little above what I would expect for that time and I really felt it in the hip flexors. Realizing that I was running too fast for the goals of the night, I focused on shortening my stride as much as I could with the quick cadence. This last mile was run at 8:59, which was 29 seconds too slow. My heart rate was around 75% for the last mile. I'm hoping that by doing a quick cadence night once a week that my average running leg turnover will increase.